Catheter positioning system

ABSTRACT

The present invention relates to a system adapted to position an ablation catheter at a location where a pulmonary vein extends from an atrium. The system includes a deflection device and a sheath and optionally uses a guidewire. An ablation catheter is disclosed for use with the positioning system, wherein the deflection device and the sheath cooperate so as to facilitate positioning of the catheter at the location.

RELATED APPLICATIONS

This application claims priority under 35 U.S.C. §119(e) to ProvisionalApplication No. 60/133,807, filed on May 11, 1999.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a system adapted to position anablation catheter at a location where a pulmonary vein extends from theleft atrium.

2. Description of the Related Art

Cardiac arrhythmia's, particularly atrial fibrillation, are a pervasiveproblem in modern society. Although many individuals lead relativelynormal lives despite persistent atrial fibrillation, the condition isassociated with an increased risk of myocardial ischemia, especiallyduring strenuous activity. Furthermore, persistent atrial fibrillationhas been linked to congestive heart failure, stroke, and otherthromboembolic events. Thus, atrial fibrillation is a major publichealth problem.

Normal cardiac rhythm is maintained by a cluster of pacemaker cells,known as the sinoatrial (“SA”) node, located within the wall of theright atrium. The SA node undergoes repetitive cycles of membranedepolarization and repolarization, thereby generating a continuousstream of electrical impulses, called “action potentials.” These actionpotentials orchestrate the regular contraction and relaxation of thecardiac muscle cells throughout the heart. Action potentials spreadrapidly from cell to cell through both the right and left atria via gapjunctions between the cardiac muscle cells. Atrial arrhythmia's resultwhen electrical impulses originating from sites other than the SA nodeare conducted through the atrial cardiac tissue.

In most cases, atrial fibrillation results from perpetually wanderingreentrant wavelets, which exhibit no consistent localized region(s) ofaberrant conduction. Alternatively, atrial fibrillation may be focal innature, resulting from rapid and repetitive changes in membranepotential originating from isolated centers, or foci, within the atrialcardiac muscle tissue. These foci exhibit consistent centrifuigalpatterns of electrical activation, and may act as either a trigger ofatrial fibrillatory paroxysmal or may even sustain the fibrillation.Recent studies have suggested that focal arrhythmia's often originatefrom a tissue region along the pulmonary veins of the left atrium, andeven more particularly in the superior pulmonary veins.

Several surgical approaches have been developed for the treatment ofatrial fibrillation. For example, Cox, J L et al. disclose the “maze”procedure, in “The Surgical Treatment Of Atrial Fibrillation. I.Summary”, Thoracic and Cardiovascular Surgery 101(3):402-405 (1991) and“The Surgical Treatment Of Atrial Fibrillation. IV. Surgical Technique”,Thoracic and Cardiovascular Surgery 101(4):584-592 (1991). In general,the maze procedure is designed to relieve atrial arrhythmia by restoringeffective SA node control through a prescribed pattern of incisionsabout the cardiac tissue wall. Although early clinical studies on themaze procedure included surgical incisions in both the right and leftatrial chambers, more recent reports suggest that the maze procedure maybe effective when performed only in the left atrium (see for exampleSueda et al., “Simple Left Atrial Procedure For Chronic AtrialFibrillation Associated With Mitral Valve Disease” (1996)).

The left atrial maze procedure involves forming vertical incisions fromthe two superior pulmonary veins and terminating in the region of themitral valve annulus, traversing the inferior pulmonary veins en route.An additional horizontal incision connects the superior ends of the twovertical incisions. Thus, the atrial wall region bordered by thepulmonary vein ostia is isolated from the other atrial tissue. In thisprocess, the mechanical sectioning of atrial tissue eliminates theatrial arrhythmia by blocking conduction of the aberrant actionpotentials.

The moderate success observed with the maze procedure and other surgicalsegmentation procedures have validated the principle that mechanicallyisolating cardiac tissue may successfully prevent atrial arrhythmia's,particularly atrial fibrillation, resulting from either perpetuallywandering reentrant wavelets or focal regions of aberrant conduction.Unfortunately, the highly invasive nature of such procedures may beprohibitive in many cases. Consequently, less invasive catheter-basedapproaches to treat atrial fibrillation through cardiac tissue ablationhave been developed.

These less invasive catheter-based therapies generally involveintroducing a catheter within a cardiac chamber, such as in apercutaneous translumenal procedure, wherein an energy sink on thecatheter's distal end portion is positioned at or adjacent to theaberrant conductive tissue. Upon application of energy, the targetedtissue is ablated and rendered non-conductive.

The catheter-based methods can be subdivided into two relatedcategories, based on the etiology of the atrial arrhythmia. First, focalarrhythmias have proven amenable to localized ablation techniques, whichtarget the foci of aberrant electrical activity. Accordingly, devicesand techniques have been disclosed which use end-electrode catheterdesigns for ablating focal arrhythmia's centered in the pulmonary veins,using a point source of energy to ablate the locus of abnormalelectrical activity. Such procedures typically employ incrementalapplication of electrical energy to the tissue to form focal lesions.

The second category of catheter-based ablation methods is designed fortreatment of the more common forms of atrial fibrillation, resultingfrom perpetually wandering reentrant wavelets. Such arrhythmias aregenerally not amenable to localized ablation techniques, because theexcitation waves may circumnavigate a focal lesion. Thus, the secondclass of catheter-based approaches have generally attempted to mimic theearlier surgical segmentation techniques, such as the maze procedure,wherein continuous linear lesions are required to completely segment theatrial tissue so as to block conduction of the reentrant wave fronts.

For the purpose of comparison, ablation catheter devices and relatedmethods have also been disclosed for the treatment of ventricular orsupraventricular tachycardias, such as disclosed by Lesh, MD in“Interventional Electrophysiology—State Of The Art, 1993” American HeartJournal, 126:686-698 (1993) and U.S. Pat. No. 5,231,995 to Desai.

While feasible catheter designs for imparting linear ablation trackshave been described, as a practical matter, most of these catheterassemblies have been difficult to position and maintain placement andcontact pressure long enough and in a sufficiently precise manner in thebeating heart to successfully form segmented linear lesions along achamber wall. Indeed, many of the aforementioned methods have generallyfailed to produce closed transmural lesions, thus leaving theopportunity for the reentrant circuits to reappear in the gaps remainingbetween point or drag ablations. In addition, minimal means have beendisclosed in these embodiments for steering the catheters to anatomicsites of interest such as the pulmonary veins.

None of the catheter-based ablation assemblies disclose a system adaptedfor positioning one end of a linear ablation element within a firstostium of a first pulmonary vein and the other end of the ablationelement within a second ostium of a second pulmonary vein. Nor does theprior art disclose a method for securing the ablation element between afirst and second anchor, thereby maintaining a desired linear positionin contact with the atrial wall and facilitating the formation of alinear ablation track along the length of tissue between the anchors.

SUMMARY OF THE INVENTION

The present invention relates to a positioning system for guiding acatheter to a location where a pulmonary vein extends from an atrium.The system comprises a deflection device, a sheath adapted to bedeflected by the deflection device, and a guidewire. The deflectiondevice can be removably engaged within the sheath. The sheath anddeflection device cooperate to facilitate positioning of the guidewirewithin the pulmonary vein when the guidewire is advanced through thesheath and into the atrium.

In accordance with this mode, the deflection device comprises apre-shaped stylet. In addition or in the alternative, the deflectiondevice comprises a pre-shaped tubular guide member.

In one variation of the positioning system, the deflection device isintegral with the sheath. The sheath preferably comprises proximal anddistal ends and a moveable pullwire attached to the distal end of thesheath. The proximal end of the sheath is adapted to facilitatemanipulation of the pullwire, such that manipulation of the pullwirecauses deflection of the distal end of the sheath.

In another variation of the positioning system, the deflection device isintegral with the catheter, wherein the catheter further comprisesproximal and distal ends and a moveable pullwire attached to the distalend of the catheter, and wherein the proximal end of the catheter isadapted to facilitate manipulation of the pullwire, such thatmanipulation of the pullwire causes deflection of the distal end of thecatheter.

In a variation to the present mode, the catheter comprises an electrodeelement. The electrode element may be a mapping electrode, an ablationelectrode, or both a mapping electrode and an ablation electrode. In onemode, the electrode element may be an RF ablation element.

Where the catheter comprises an ablation element, the ablation elementmay be selected from the group consisting of a microwave ablationelement, a cryogenic ablation element, a thermal ablation element, alight-emitting ablation element, and an ultrasound transducer. Theablation element may be adapted to form a linear lesion, acircumferential lesion, or both.

In a variation to this mode, the guidewire may be selected from thegroup consisting of a guidewire, an anchor wire, and a deflectableguidewire. The anchor wire comprises an elongate body with proximal anddistal end portions and having an expandable member along the distal endportion, such that radial expansion of the expandable member is adaptedto anchor the guidewire within the pulmonary vein.

In accordance with another mode of the present invention, a positioningsystem is disclosed for guiding an ablation catheter to a location wherea lumen extends from a body cavity. The positioning system comprises adeflection device and a transeptal sheath. The deflection device isadapted to be removably engaged within the sheath, whereby the sheathand deflection device cooperate to facilitate positioning of theablation catheter at.the location when the catheter is advanced throughthe sheath and into the body cavity and guided toward the location.

The deflection device may comprise a pre-shaped stylet or a pre-shapedtubular guide member. The deflection device may also be integral withthe sheath, wherein the sheath comprises proximal and distal ends and amoveable pullwire attached to the distal end of the sheath, and whereinthe proximal end of the sheath is adapted to facilitate manipulation ofthe pullwire, such that manipulation of the pullwire causes deflectionof the distal end of the sheath.

In a variation to this mode, the deflection device is integral with thecatheter, wherein the catheter further comprises proximal and distalends and a moveable pullwire attached to the distal end of the catheter,and wherein the proximal end of the catheter is adapted to facilitatemanipulation of the pullwire, such that manipulation of the pullwirecauses deflection of the distal end of the catheter.

The ablation catheter comprises an ablation element, which may beselected from the group consisting of a microwave ablation element, acryogenic ablation element, a thermal ablation element, a light-emittingablation element, and an ultrasound transducer. The ablation element maybe adapted to form a linear lesion, a circumferential lesion, or both.

In accordance with another mode of the present invention, a positioningsystem is disclosed for guiding an ablation catheter to a location wherea pulmonary vein extends from an atrium. The system comprises adeflection device and a transeptal sheath having proximal and distalends, wherein the deflection device is removably positionable within thetranseptal sheath without extending beyond the distal end of the sheath.

In a variation to this mode of the invention, the deflection devicecomprises a pre-shaped stylet. In addition or in the alternative, thedeflection device may comprise a pre-shaped tubular guide member.

In another variation of the positioning system, the deflection device isintegral with the sheath. The sheath preferably comprises proximal anddistal ends and a moveable pullwire attached to the distal end of thesheath. The proximal end of the sheath is adapted to facilitatemanipulation of the pullwire, such that manipulation of the pullwirecauses deflection of the distal end of the sheath.

In another variation of the positioning system, the deflection device isintegral with the catheter, wherein the catheter further comprisesproximal and distal ends and a moveable pullwire attached to the distalend of the catheter, and wherein the proximal end of the catheter isadapted to facilitate manipulation of the pullwire, such thatmanipulation of the pullwire causes deflection of the distal end of thecatheter.

In another variation of the present mode, the catheter comprises anelectrode element. The electrode element may be a mapping electrode, anablation electrode, or both a mapping electrode and an ablationelectrode. In one mode, the electrode element may be an RF ablationelement.

Where the catheter comprises an ablation element, the ablation elementmay be selected from the group consisting of a microwave ablationelement, a cryogenic ablation element, a thermal ablation element, alight-emitting ablation element, and an ultrasound transducer. Theablation element may be adapted to form a linear lesion, acircumferential lesion, or both.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a variation of the guiding introducer ofthe present invention in which the introducer has a slit that extendsalong the entire length of the tubular member.

FIGS. 2A-D are transverse cross-sectional views, taken along line 2—2,showing various configurations for the longitudinal slit.

FIG. 3 is a perspective view of a variation of the peel-away guidingintroducer, in which the guiding introducer is mounted on the distal endof a mandrel.

FIG. 4 is a perspective view of a deflectable guidewire in accordancewith the present invention.

FIG. 5 is a perspective view of another variation of the deflectableguidewire of the present invention having a removable handle.

FIG. 6 is a schematic view of a variation of the positioning system ofthe present invention showing a deflectable guidewire slideably engagedwithin a preshaped guiding introducer slideably engaged within atranseptal sheath.

FIG. 7 is a schematic view of a variation of the catheter positioningsystem of the present invention in situ, showing the distal end of theablation catheter tracking over a balloon anchor wire into the firstpulmonary vein and a preshaped guiding introducer extending from asecond guidewire port in the ablation catheter and directing a secondguidewire into the second pulmonary vein.

FIG. 8 is a schematic view of another variation of the catheterpositioning system of the present invention in situ, showing the distalend of the ablation catheter tracking over the balloon anchor wire intothe first pulmonary vein and a deflectable guidewire extending from asecond guidewire port in the ablation catheter and cannulating thesecond pulmonary vein.

FIG. 9 is a longitudinal cross-sectional view of an anchor device inaccordance with a preferred mode of the present invention, showing anover-the-wire catheter with an ultrasound ablation element positionedalong the distal end portion within an expandable member.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The invention relates to a system for positioning an ablation catheterwithin the left atrium. More specifically, the positioning system of thepresent invention is adapted to position and anchor the distal end of anablation element within the first ostium of a first pulmonary vein andthe proximal end of the ablation element within the second ostium of asecond pulmonary vein. Preferably, the system includes a transeptalsheath inserted through an atrial septum that separates a right atriumfrom a left atrium. In one variation, a guiding introducer slideablyengaged within the transeptal sheath has a preshaped distal portionadapted to point toward the first ostium of the first pulmonary vein.The preferred positioning system also incorporates a balloon anchor wirethat is advanced through the preshaped guiding introducer and into thefirst pulmonary vein. The balloon anchor wire is anchored within thepulmonary vein by inflating a balloon on the distal end of the balloonanchor wire. The preshaped guiding introducer can then be retracted andremoved from the balloon anchor wire by sliding off the proximal end orin a variation, by peeling away from the balloon anchor wire.

Alternatively, the balloon anchor wire may be replaced by a conventionalguidewire or preferably, a deflectable guidewire adapted to permit theuser to control the deflection of the distal portion, such that thedeflectable guidewire can be advanced and steered into position forengaging the first pulmonary vein. The deflectable guidewire may beinserted either directly through the transeptal sheath or through apreshaped guiding introducer slideably engaged in the transeptal sheath.Deflection of the distal portion of the guidewire, once within the firstpulmonary vein, may serve to anchor the guidewire within the pulmonaryvein. In this case, the deflectable guidewire would take the place ofthe balloon anchor wire described above.

The ablation catheter in accordance with the present invention has anablation element with an ablation length extending proximally from thedistal portion of the ablation catheter. The ablation catheter isadapted to slideably engage the balloon anchor wire or the deflectableguidewire within an internal passageway or an external sleeve, theguidewire tracking means having a distal port located distal to thedistal end of an ablation element. The ablation catheter may beintroduced into the left atrium by tracking over the balloon anchor wireor the deflectable guidewire, whereby advancing the ablation catheterover the balloon anchor wire or the deflectable guidewire causes thedistal end of the ablation element to engage the first pulmonary vein.

The ablation catheter preferably also has a second guidewire trackingmeans, comprising either an internal passageway or an external sleeve,with a second port located proximal to the proximal end of the ablationelement. In one variation, a second guidewire preloaded and slideablyengaged within the second guidewire passageway of the ablation cathetermay be advanced directly out of the second guidewire port and into thesecond pulmonary vein.

Preferably, a second preshaped guiding introducer, preloaded andslideably engaged within the second guidewire passageway of the ablationcatheter is advanced out of the proximal guidewire port and positionedin such a manner as to direct the second guidewire, slideably engagedwithin the guiding introducer, toward the second pulmonary vein. Thesecond guiding introducer may optionally be advanced into the ostium ofthe second pulmonary vein, thereby insuring that the second guidewirecannulates the vein.

Alternatively, a steerable, deflectable guidewire may be preloaded andslideably engaged within the second guidewire passageway in the ablationelement. In this variation, the proximal end of the deflectableguidewire is adapted to permit the user to control the deflection of thedistal portion, such that the deflectable guidewire can be advanced andsteered into position for engaging the second pulmonary vein. Deflectionof the distal portion of the deflectable guidewire once within thesecond pulmonary vein may anchor the guidewire and thereby provide abetter placement of the proximal end of the ablation element.

In another embodiment, the second guidewire may be fed into the secondpulmonary vein prior to introducing the ablation catheter. A secondguiding introducer with a preshaped distal end adapted to point towardthe second pulmonary vein may be used to advance the second guidewireinto the pulmonary vein. Where a balloon anchor wire and a guidewirehave been positioned within the respective first and second pulmonaryveins, the ablation catheter may then be inserted over the two wires andfed into the left atrium through the transeptal sheath. Advancing thedistal portion of the ablation catheter over the:.balloon anchor wire,which is anchored within the first pulmonary vein, causes the distal endof the ablation element to be positioned within and anchored to thefirst ostium of the first pulmonary vein. Further advancing the ablationcatheter over the second guidewire which is located within the secondpulmonary vein causes the proximal end of the ablation element to engagethe second ostium of the second pulmonary vein, thereby securing theablation length against the atrial wall between the first and secondpulmonary vein ostia.

It is contemplated that the subject matter disclosed herein may becombined with various embodiments which have formed the subject matterof other contemporaneous or previous patent filings, including withoutlimitation the embodiments shown and described in the following issuedpatents and filed provisional and non-provisional U.S. PatentApplications:

(1) U.S. patent application Ser. No. 08/853,861 filed May 9, 1997 for“Tissue Ablation Device And Method Of Use”, now U.S. Pat. No. 5,971,983;

(2) U.S. patent application Ser. No. 08/889,798 filed Jul. 8, 1997 for“Circumferential Ablation Device Assembly”, now U.S. Pat. No. 6,024,740;

(3) U.S. patent application Ser. No. 08/889,835 filed Jul. 8, 1997 for“Device And Method For Forming A Circumferential Conduction Block In APulmonary Vein”, now U.S. Pat. No. 6,012,457;

(4) U.S. patent application Ser. No. 09/073,907 filed May 06, 1998 for“Tissue Ablation Device With Fluid Irrigated Electrode”;

(5) U.S. patent application Ser. No. 09/199,736 filed Nov. 25, 1998 for“Circumferential Ablation Device Assembly”;

(6) U.S. patent application Ser. No. 09/240,068 filed Jan. 29, 1999 for“Device And Method For Forming A Circumferential Conduction Block In APulmonary Vein”;

(7) U.S. patent application Ser. No. 09/260,316 filed Mar. 1, 1999 for“Tissue Ablation System And Method For Forming Long Linear Lesion”;

(8) Provisional U.S. Application No. 60/122,571, Filed on Mar. 2, 1999for “Feedback Apparatus And Method For Ablation At Pulmonary VeinOstium”;

(9) Provisional U.S. Application No. 60/125,509, filed Mar. 19, 1999 for“Circumferential Ablation Device Assembly And Methods Of Use AndManufacture Providing An Ablative Circumferential Band Along AnExpandable Member”;

(10) Provisional U.S. Application No. 60/125,928, filed Mar. 23, 1999for “Circumferential Ablation Device Assembly And Methods Of Use AndManufacture Providing An Ablative Circumferential Band Along AnExpandable Member”;

(11) Provisional U.S. Application No. 60/133,610, filed May 11, 1999 for“Balloon Anchor Wire”;

(12) Provisional U.S. Application No. 60/133,680, filed May 11, 1999 for“Apparatus And Method Incorporating An Ultrasound Transducer”;

(13) Provisional U.S. Application No. 60/133,677, filed May 11, 1999 for“Tissue Ablation Device Assembly And Method For Electrically Isolating APulmonary Vein Ostium From A Posterior Left Atrial Wall”; thedisclosures of these references are herein incorporated in theirentirety by reference.

Preshaped Guiding Introducer

With reference to FIG. 1, there is shown a perspective view of a“peel-away” variation of the guiding introducer 10. The guidingintroducer 10 consists of a tubular member 12 with a preshaped distalregion 14 and a removable hub 16 on the proximal end 18 of the tubularmember. The tubular member 12 has a slit 20 that extends along theentire length of the tubular member. The distal region 14 of the guidingintroducer is preshaped so that the distal orifice 22 can be positionedto point toward a selected pulmonary vein by adjustably advancing andretracting the guiding introducer 10 through a transeptal sheath and bytorquing the proximal end 18 of the guiding introducer.

The guiding introducer in accordance with the present invention may haveany shape consistent with the purpose of the guiding introducer todirect a guidewire toward a predetermined pulmonary vein. Once theguidewire has been placed in the pulmonary vein, the guiding introducershown in FIG. 1 is adapted to be peeled away from the guidewire byremoving the proximal hub and opening the tubular member along thelongitudinal slit 20. FIGS. 2A-D are transverse cross-sectional views,taken along line 2—2, showing various configurations for thelongitudinal slit. In other embodiments, the guiding introducer can beretracted and removed from the coaxially engaged guidewire by slidingoff the proximal end of the guidewire.

The tubular member, or parts thereof, could be fashioned from a widevariety of polymeric materials including, polyimide, nylon, Pebax,polyethylene, or PVC. The proximal shaft could be made from stiffermaterials such as nickel titanium or stainless steel. The shaft could beof composite construction, incorporating braided strands that helpprovide torque transmission. Such strands could consist of materialsincluding flat or round metallic wire (i.e., stainless steel), dacronand kevlar.

The tubular guiding introducer may have a permanently mounted luer onthe proximal end that allows easy front-loading of the guidewire andflushing of the lumen. However, backloading of the ablation catheterover the guiding introducer may be preferred, requiring a removable (ornone at all) proximal hub or adapter, as illustrated in FIG. 1. Such aremovable hub or adapter could consist of a luer with collapsible O-ringseal.

Dimensions of the device would depend on the guidewire beingaccommodated. Typical guidewires to be used would range in diameter fromabout 0.014″ to 0.038″. The interior lumen typically adds about 0.004″to 0.010″ to these sizes. Wall thicknesses could range from about 0.002″to 0.012″. Device length would range from about 90 cm to about 300 cmdepending on the need for backloading the catheter device over theguiding introducer. The outer diameter of the guiding introducer isapproximately 5-10 F, preferably about 7 F, thereby permitting theguiding introducer to enter the left atrium by sliding within atranseptal sheath. Where the guiding introducer is to be employed forguiding the second guidewire into the second pulmonary vein, the outerdiameter of the guiding introducer is preferably about 4-5 F, therebypermitting the guiding introducer to slide within the second guidewirepassageway in the ablation catheter and exit the ablation catheter viathe second guidewire port.

With reference to FIG. 3, there is shown another variation of apeel-away guiding introducer of the present invention in which amonorail guide system is employed. The proximal end 26 of the tubularmember 12 is secured to the distal end 24 of a mandrel or hypotube 28.As described above with reference to FIG. 1, the distal region 14 ispreshaped to point toward a predetermined site and the tubular memberhas a longitudinal slit 20 to facilitate peel-away removal. The guidingintroducer 10, preloaded with a guidewire, is advanced through thetranseptal sheath. The guide can be advanced, retracted and/or torquedif necessary by manipulation of the mandrel or hypotube 28 to direct thedistal opening 22 toward the selected pulmonary vein. The guidewire isthen advanced directly into the vein. The guide is adapted to be removedby partially retracting and peeling away from-the guidewire.

Deflectable Member

An embodiment of the positioning system may employ a deflectable member.Devices such as deflectable guidewires are commercially available. Withreference to FIG. 4, the deflectable guidewire 30 consists of a tubularwire wound coil 32 surrounding a moveable pullwire (not shown) attachedto the coil at the distal end. A flattened member (not shown) is alsotypically incorporated into the distal lumen. Manipulation of thecorewire by operation of the control lever 34 mounted on the handle 36that is attached to the proximal end 37 of the deflectable guidewire 30causes the tubular wire wound coil 32 to compress and deflect.

Another variation of the positioning system of the present invention mayemploy a deflectable member with a removable handle, as shown in FIG. 5.With reference to FIG. 5, the deflectable guidewire 38 consists of atubular member 40 made from a wire wound coil surrounding a moveablepullwire. The distal end of the pullwire (not shown) is attachedinternally to the distal end 42 of the tubular member 40. The proximalend 44 of the pullwire, which extends beyond the externally threadedproximal end 46 of the tubular member 40, has a enlarged stop or ball 48that is engaged within a recess 50 in the shaft 52 of a pullknob 54. Theshaft 52 of the pullknob 54 is slideably engaged within a bore 56 in theproximal region 58 of a handle 60. The distal region 62 of the handle 60is tapered and includes an internally threaded hole 64 adapted toreceive the externally threaded proximal end 46 of the tubular member40. Pulling on the pullknob 54 causes the tubular member 40 to deflect.

Balloon anchor wire

In a preferred variation of the present invention, a balloon anchor wireis placed in the first pulmonary vein in order to serve as a guide forthe distal end of the ablation element. An exemplary balloon anchor wirein accordance with the present invention is described in pendingprovisional application Ser. No. 60/133,610, herein incorporated byreference. The balloon anchor wire consists of a tubular member with aballoon attached to the distal region of the tubular member. The tubularmember is fitted over an integral corewire. The corewire extends throughthe entire length of the tubular member, providing support (e.g.,enhancing push force and kink resistance). The distal region of thecorewire is tapered providing greater flexibility to the distal regionof the tubular member. The distal end of the corewire is bonded to thedistal end of the tubular member. The bond between the corewire and thetubular member is airtight, so that the balloon can be inflated. A wirecoil may be placed over the distal end of the corewire to help providesupport to the corewire and prevent kinking. Preferably, the wire coilprotrudes distally from the balloon to aid in atraumatic navigation ofvessel branches.

Where the corewire extends only partially through the tubular member, itmay terminate anywhere proximal to the balloon. In this variation, thetubular member may comprise distinct proximal, intermediate, and distalregions, in which the corewire terminates in the proximal region of thetubular member. In such case, the proximal region of the tubular memberis constructed of a heavier gage polymer, capable of providing thenecessary push force and kink resistance, which is provided by thecorewire in the continuous corewire design.

The wall of the distal region of the tubular member, which is supportedby the integral corewire, is composed of a relatively thick layer (about0.005″ to about 0.015″, preferably about 0.010″ to 0.012″) of lowdensity polymer, such as polyethylene, from which the balloon is formed.In contrast, the wall of the intermediate region of the tubular member,which is also supported by the integral corewire, is composed of a muchthinner layer (about 0.001″ to about 0.010″, preferably about 0.004″ to0.005″) of a higher density polymer, such as polyimide. The wall of theproximal region of the tubular member, which is not supported by anunderlying corewire, is composed of the same high density polymer as theintermediate region, but of a thickness (about 0.005″ to about 0.015″,preferably about 0.010″ to 0.012″) like that of the distal region. Thethicker gage high-density polymer construction is necessary in theproximal region absent a continuous corewire, in order to providesufficient pushing force. In the preferred continuous corewire design,the walls of the tubular member may be constructed out of the samepolymeric material of approximately the same gage along the entirelength of the balloon anchor wire. Consequently, there may be nodistinct regions, having instead only relative proximal and distalregions.

The inside diameter of the tubular member is sufficiently large inrelation to the outer diameter of the corewire along the entire lengthof the tubular member that an inflation lumen is created between theinner wall of the tubular member and the outer surface of the corewirein the intermediate and distal regions of the tubular member. In theproximal region, where no corewire is present, the inflation lumencomprises the entire lumen of the tubular member. In another variationof the balloon anchor wire, a separate inflation lumen may reside withinthe balloon anchor wire or along the outside of the balloon anchor wire.An inflation medium (i.e., air, saline or contrast) can be passedthrough the inflation lumen to inflate the balloon.

An over-the-wire variation of the balloon anchor wire of the presentinvention consists of a tubular member and a distally located balloon.However, a guidewire is slideably engaged within a guidewire passagewaythat runs longitudinally through the entire length of the balloon anchorwire. An inflation lumen is also present between the inner wall of thetubular member and the outer wall of the guidewire passageway to permitballoon inflation and deflation as described above.

The balloon anchor wire of the present invention has a removable adapteron its proximal end. The shaft of the balloon anchor wire has a proximalend that is inserted into the distal end of the adapter and is engagedtherein by a distal O-ring. The distal O-ring can be adjustablytightened and loosened on the proximal end of the shaft by turning thedistal knob that is threaded onto the distal end of the adapter. Thecorewire may exit the proximal end of the adapter. A proximal O-ringengages the corewire. The proximal O-ring can be adjustably tightenedand loosened on the corewire by turning the proximal knob that isthreaded onto the proximal end of the adapter. A fluid port is in fluidcommunication with the inflation lumen created between the outer surfaceof the corewire and the inner wall of the tubular member, therebyallowing inflation and deflation by conventional means of the balloonalong the distal region of the balloon anchor wire when the proximal anddistal O-rings are tightened.

Linear Ablation Catheter

Exemplary variations of the tissue ablation catheter comprise theablation assemblies described in pending application Ser. Nos.09/260,316 and 09/073,907, the disclosures of which are hereinincorporated by reference. The ablation assembly includes an irrigatedablation member that is attached to a delivery member in order to accessand position the ablation member at the site of the target tissue. Thedelivery member may take the form of an over-the-wires catheter, whereinthe “wires” include first and second guidewires. Preferably, the firstguidewire is a balloon anchor wire or a deflectable guidewire.Alternatively, the wires may be engaged by external tracking sleeves.The delivery member comprises an elongated body with proximal and distalend portions. As used herein, the terms “distal” and “proximal” are usedin reference to a source of fluid located outside the body of thepatient. The elongated body preferably includes a first guidewire lumen,a second guidewire lumen, an electrical lead lumen and a fluid lumen, asdescribed in greater detail below.

Each lumen extends between a proximal port and a respective distal end.The distal ends of the lumens extend through the ablation member, asdescribed in greater detail below. Although the wire, fluid andelectrical lead lumens may assume a side-by-side relationship, theelongated body can also be constructed with one or more of these lumensarranged in a coaxial relationship, or in any of a wide variety ofconfigurations that will be readily apparent to one of ordinary skill inthe art.

The elongated body of the delivery member and the distally positionedablation member desirably are adapted to be introduced into the leftatrium, preferably through the transeptal sheath. Therefore, the distalend portion of the elongated body and the ablation member aresufficiently flexible and adapted to track over and along the guidewirespositioned within the left atrium, and more preferably seated within twoof the pulmonary veins that communicate with the left atrium. In anexemplary construction, the proximal end portion of the elongated bodyis constructed to be at least 30% stiffer than the distal end portion.According to this relationship, the proximal end portion may be suitablyadapted to provide push transmission to the distal end portion while thedistal end portion and the ablation member are suitably adapted to trackthrough bending anatomy during in vivo delivery of the ablation memberinto the desired ablation region.

A more detailed construction for the components of the elongated body,which is believed to be suitable for use in transeptal left atrialablation procedures, is as follows. The elongated body itself may havean outer diameter provided within the range of from about 3 French toabout 11 French, and more preferably from about 7 French to about 9French. Each wire lumen may be adapted to slideably receive a preshapedguiding introducer. Further the wire lumens are adapted to slideablyreceive a balloon anchor wire, a conventional guidewire and/or adeflectable guidewire ranging from about 0.010″ to about 0.038″ indiameter, and preferably are adapted for use with guidewires rangingfrom about 0.018″ to about 0.035″ in diameter. Where a 0.035″ diameterballoon anchor wire is to be used, the balloon anchor wire lumendesirably has an inner diameter of 0.040″ to about 0.042″. In addition,the fluid lumen desirably has an inner diameter of about 0.019″ in orderto permit ample irrigation of the ablation member.

The elongated body comprises an outer tubular member that preferablyhouses an electrical lead tubing, a fluid tubing, a first guidewiretubing and a second guidewire tubing. Each of the tubings extends atleast from the proximal end portion of the elongated body to the distalend portion, and at least partially through the ablation member, asdescribed below. The tubings are arranged in a side-by-side arrangement;however, as noted above, one or more of the tubings can be arranged in acoaxial arrangement. Moreover, one or both of the wire tracking meanscould be located outside of the tubular member, as tubular sleeves. Inone mode, the inner tubings are polyimide tubes. Such tubing isavailable commercially from Phelps Dodge, of Trenton, Ga. The electricallead and fluid tubings desirably have a 0.019″ inner diameter and a0.023″ outer diameter, while the wire tubings are slightly larger, asindicated above. The outer tubular member comprises a thermoplastic,such as, for example, a urethane or vinyl material. A suitable materialfor this application is Pebax of a grade between 3533 to 7233, and of anouter diameter of about 0.064″.

Notwithstanding the specific delivery device constructions justdescribed, other delivery mechanisms for delivering the ablation memberto a desired ablation region are also contemplated. For example, whilean “over-the-wire” catheter construction was described, other guidewiretracking designs may also be suitable substitutes, such as for examplecatheter devices known as “rapid exchange” or “monorail” variationswherein the guidewire is only housed within a lumen of the catheter inthe distal regions of the catheter. In another example, a deflectabletip design may also be a suitable substitute. The latter variation canalso include a pullwire which is adapted to deflect the catheter tip byapplying tension along varied stiffness transitions along the catheter'slength, as described above.

The proximal end portion of the elongated body terminates in a coupler.In general, any of several known designs for the coupler would besuitable for use with the present tissue ablation device assembly, aswould be apparent to one of ordinary skill. For example, a proximalcoupler may engage the proximal end portion of the elongated body of thedelivery member. The coupler includes an electrical connector thatelectrically couples one or more conductor leads, which stem from theablation member and extend through the electrical lead tube, with anablation actuator. The coupler also desirably includes anotherelectrical connector that electrically couples one or more temperaturesensor signal wires to a controller of the ablation actuator.

As known in the art, the ablation actuator is connected to both of theelectrical connectors and to a ground patch. A circuit thereby iscreated which includes the ablation actuator, the ablation member, thepatient's body, and the ground patch that provides either earth groundor floating ground to the current source. In the circuit, an electricalcurrent, such as a radiofrequency, (“RF”) signal may be sent through thepatient between the ablation member and the ground patch, as well knownin the art.

The coupler may also include a fluid coupler. The fluid coupler isadapted to be coupled to a source of pressurized fluid (e.g. salinesolution) so as to irrigate the ablation member, as described below. Thefluid coupler communicates with the fluid tube to supply the ablationmember with a source of pressurized fluid.

The ablation member has a generally tubular shape and includes anablation element. The phrase “ablation element” as used herein means anelement that is adapted to substantially ablate tissue in a body spacewall upon activation by an actuator. The terms “ablate” or “ablation,”including derivatives thereof, are hereafter intended to mean thesubstantial altering of the mechanical, electrical, chemical, or otherstructural nature of tissue. In the context of intracardiac ablationapplications, “ablation” is intended to mean sufficient altering oftissue properties to substantially block conduction of electricalsignals from or through the ablated cardiac tissue. The term “element”within the context of “ablation element” is herein intended to mean adiscrete element, such as an electrode, or a plurality of discreteelements, such as a plurality of spaced electrodes, which are positionedso as to collectively ablate a region of tissue. Therefore, an “ablationelement” according to the defined terms may include a variety ofspecific structures adapted to ablate a defined region of tissue. Forexample, one suitable ablation element for use in the present inventionmay be formed, according to the teachings of the embodiments below, froman “energy emitting” type that is adapted to emit energy sufficient toablate tissue when coupled to and energized by an energy source.

Suitable “energy emitting” ablation elements for use in the presentinvention may therefore include, for example, but without limitation: anelectrode element adapted to couple to a direct current (“DC”) oralternating current (“AC”) current source, such as a radiofrequency(“RF”) current source; an antenna element which is energized by amicrowave energy source; a heating element, such as a metallic elementor other thermal conductor which is energized to emit heat such as byconvection or conductive heat transfer, by resistive heating due tocurrent flow, a light-emitting element (e.g., a laser), or an ultrasonicelement such as an ultrasound crystal element which is adapted to emitultrasonic sound waves sufficient to ablate a circumferential region oftissue when coupled to a suitable excitation source. It also isunderstood that those skilled in the art can readily adapt other knownablation devices for use with the present irrigated ablation member.

In a preferred mode, the ablation element includes a plurality ofelectrodes that are arranged over a length of the ablation member nextto one another (i.e., are arranged in series in the spatial sense). Thelength from the proximal-most electrode to the distalmost electrodedefines an ablation length, which is less than a working length of theablation element, as described below.

At least one conductor lead connects to the electrodes. The number ofconductor leads is desirably equal to the number of electrodes to allowfor independent control of each electrode under some modes of operation.Each conductor is a 36 AWG copper wire insulated with a 0.0005″ thickpolyimide coating. Each conductor exits the electrical lead tube at apoint near a corresponding electrode. A distal end of each wire isexposed and is electrically coupled to the corresponding electrode inthe manner described below. The proximal end of each conductor lead isconnected to the electrical connector on the proximal end of the tissueablation device assembly.

In one embodiment, an irrigation mechanism may be employed to irrigatethe ablation element. The irrigation mechanism is adapted to provide agenerally even flow of fluid about each of the electrodes along thelength of the ablation member. The irrigation mechanism can beconfigured to discharge fluid either in a radial direction (i.e.,generally normal to the longitudinal axis) or in the longitudinaldirection, or in both directions, as illustrated by the below describedvariations of the ablation member.

The irrigation mechanism desirably includes an inner space definedwithin a porous, fluid-permeable membrane. The membrane desirably has agenerally tubular shape and extends along at least a portion of theablation member's length; however, the membrane need not be tubular orcover the entire ablation member. The membrane though preferably isarranged to face the target tissue once the ablation element isdelivered to and positioned within the particular body space. Themembrane has a length, as measured in the longitudinal direction, whichis greater than a distance between the proximal-most and distal-mostelectrodes of the series. The membrane's length is defined between itsproximal and distal ends.

The porous membrane includes an inner surface and an outer surface thatdefine the boundaries of a porous wall. The wall is formed of a porous,biocompatible, generally non-compressible material. As used herein, theterm “non-compressible” means that the material generally does notexhibit appreciable or sufficient compressibility between its inner andouter surfaces to conform to surface irregularities of the tissueagainst which the ablation member is placed. The material, however, issufficiently flexible in the longitudinal direction (i.e., deflectable)so as to track over and along the first and second guidewires positionedwithin the left atrium, and more preferably seated within two of thepulmonary veins that communicate with the left atrium. In other words,the material of the tubular porous membrane allows it to bend through awinding access path during in vivo delivery of the ablation member intothe desired ablation region.

The porous nature of the membrane's material also permits a fluid topass through the membrane upon the application of a sufficient pressuredifferential across the membrane. Fluid thus does not freely flowthrough the membrane. The degree of porosity of the membrane over itslength also desirably is uniform. This uniformity coupled with the flowrestrictiveness of the material results in the fluid emanating from themember in a generally even flow over the entire membrane outer surface.

Exemplary porous materials suitable for this application includeexpanded polytetrafluoroethylene (PTFE), porous polyethylene, poroussilicon, porous urethane, and tight weaves of Dacron. Such porousmaterials are formed using conventional techniques, such as, for exampleby blowing the material or by drilling micro holes within the material.The porosity of the material desirably ranges between about 5 and 50microns. An acceptable form of the porous PTFE material is availablecommercially from International Polymer Engineering, of Tempe, Ariz., asProduct Code 014-03. It has been found that fluid will pass through thismaterial upon applying a relatively low pressure within the material(e.g., 5 psi). In an exemplary form, the membrane is formed of a tubularextrusion of this material which has an inner diameter of about 0.058″and an outer diameter of about 0.068″ for applications involvingablation of myocardial tissue via an arterial or venous access path. Forother applications, such as, for example, ablation within small coronaryvessels, a significantly smaller diameter size can be used.

The porous membrane is attached to the distal end portion of thedelivery member, as noted above. The proximal end of the porous membraneis interposed between the distal end portion of the elongated body and asealing member. That is, the tubular proximal end of the porous memberis placed over the distal end of the elongated body outer tube. Thesealing member then is slipped over this assembly and arranged to liegenerally above the overlapping sections of the tube and the membrane.

The sealing member desirably is formed of a material similar to orcompatible with the material of the elongated body in order to heat-meltbond these two components together. In an exemplary form, the sealingmember comprises Pebax of a similar grade used for the outer tube of theelongated body. This bonding process occurs with the proximal end of theporous member positioned between the outer tube distal end and thesealing member.

The porous membrane also desirably includes one or more openings thatextend through the wall of the porous membrane. These openings areformed (e.g., punched) on the proximal end of the membrane prior to thebonding procedure, and can take the form of holes or longitudinal slotsthat extend into the membrane from the proximal end; of course, othershapes of openings can also be used. The similar plastic materials ofthe seal member and the elongated body outer tube fuse together withinthese openings and bond under and over the porous material of themembrane during the bonding process. This coupling securely attaches theporous membrane to the distal end portion of the elongated body.

The porous membrane of course can be joined to the distal end portion ofthe elongated body in any of a variety of other ways well known to thoseskilled in the art. For instance, the proximal end of the porousmembrane can be bonded to the outer tube distal end using abiocompatible adhesive, such as, for example, cyanoacrylate availablecommercially from Loctite® of Rockyhill, Conn., as Part No. 498.

An end cap closes the distal end of the porous membrane. The end capdesirably has a tapering shape that decreases in diameter distally. Onits distal end, the end cap includes a port that aligns with the distalend of the first guidewire tube when assembled. The end cap alsoincludes an inner opening defined in part by a collar section. The innerdiameter of the collar section is sized to receive the distal ends ofthe tubings and the outer diameter of the collar is sized to slip withinthe distal end of the porous membrane.

The end cap desirably is formed of a biocompatible plastic material,such as, for example, urethane or vinyl. In a preferred mode, the endcap is formed of same material that comprises the outer tube of theelongated body, such as, Pebax of a grade between 3533 to 7233, and ofan outer diameter of about 0.064″.

The end cap and the distal end of the porous membrane desirably aresecured together in a similar fashion to that described above. As such,a heat melt bond is formed between a second sealing member and thedistal end cap, with the distal end of the porous member beinginterposed between these elements. The similar plastic materials of thesealing member and the end cap fuse together within openings in theporous membrane at its distal end, as well as over and under the porousmembrane. Other bondings can also be used as described above.

The first guidewire tube, the second guidewire tube, the fluid tube, andthe lead wire tube each extend within the porous membrane in alongitudinal direction toward the distal end cap.

The electrical lead tube functions as a wiring harness and carries oneor more conductors or wires that are attached to the electrodes. Thetube extends beyond the distal end portion of the elongated body,through the porous membrane and terminates at a point within the distalend cap. A plug seals the distal end of the electrical lead tube. In anexemplary form, the plug is formed by filling the distal end of the tubewith Cyanoaerylat®.

The first guidewire tube preferably extends entirely through theablation member and the distal end cap, and communicates with a distalport formed in the end cap. The distal port is sized to receive aballoon anchor wire over which the elongated body and the ablationmember preferably track. The port, thus, allows a first guidewire andpreferably a balloon anchor wire to pass through the end cap. In avariation, the first guidewire tube can replace the end cap with theporous membrane attaching directly to the tube. In such an embodiment,the other tube will stop short of the distal end of the ablation member.

The second guidewire tube extends only partially through the ablationmember, and communicates with a second, distal port formed in theablation member located proximal to the proximal end of the ablationelement. The second guidewire port is sized to receive a guidingintroducer as well as the second guidewire or deflectable guidewire overwhich the ablation member tracks. The port, thus, allows the guidingintroducer and the guidewire to pass out of the ablation member.

The fluid tube defines a pressurizable fluid passageway. The fluid tubeextends beyond the distal end portion of the elongated body, through theporous membrane and terminates at a point within the distal end cap nextto a distal end of the electrical lead tube. Another plug seals thedistal end of the fluid tube. In an exemplary form, the plug is formedby filling the distal end of the tube with Loctite®. The tube, however,can terminate proximal of the electrodes but distal of the proximalmembrane seal.

The fluid tube includes at least one opening which opens into the innerspace defined within the porous membrane. In this manner, thepressurizable fluid passageway or lumen provided by the irrigation tubecommunicates with the inner space of the ablation member. A single slotis formed near a proximal end of the inner space; however, several slotsor holes can be formed along the section of the irrigation tube thatextends through the inner space.

A proximal end of the inner space desirably is sealed to prevent a flowof fluid proximally. In the present variation, the distal end of theinner space is also sealed. This allows the pressure within the innerspace to be increased to promote fluid weeping through the wall of theporous membrane, as described in greater detail below. Theabove-described sealing technique provides an adequate seal. In thealternative, a seal can be formed at each location by heat shrinkingpolyethylene teraphthalate (PET) over the tubes. The proximal seal hasan outer diameter of a sufficient size to plug the passage through theelongated body at the distal end of the body and the distal seal has anouter diameter of sufficient size to plug the opening defined by thecollar in the distal end cap.

Each electrode in the ablation element comprises a wire coil formed in ahelical pattern. The electrodes desirably have identical configurations,and thus, the following description of one is understood to applyequally to all, unless indicated otherwise.

Each coil electrode has a sufficiently large inner diameter to receivetubings, while its outer diameter is sized to fit within the tubularporous membrane. In an exemplary form, each ablation element comprises a0.005″ diameter wire made of a biocompatible material (e.g., stainlesssteel, platinum, gold-plated nitinol, etc.). The wire is unshielded andis wound in a helical fashion with about a 0.048″ inner diameter. Thecoils are spaced along the lengths of the tubings that extendlongitudinally through the porous membrane. In an exemplary mode, eachcoil has a length, as measured in the longitudinal direction, of about0.28″ and is spaced from an adjacent coil by a distance of about 0.08″.

The corresponding conductor wire passes through a hole in the electricallead tubing and is soldered to the coil with a 95 Ag/5 Sn. The conductorwire can also be electrically connected to the electrodes by othermeans, such as, for example, by resistant, ultrasonic or laser welding.In addition, the coil and the conductor can be unitary by winding thedistal end of the conductor in a helical pattern. Known electricalconnectors can also be used to electrically couple the conductor to thecorresponding electrode.

The electrodes of the ablation member desirably have sufficientflexibility to bend to track through a venous or arterial access path toan ablation target site. The electrodes can have a variety ofconfigurations as long as they afford similar flexibility. For instance,the electrode can have a tubular or cylindrical shape formed by aplurality of braided wires. The end bands link the ends of the wirestogether to prevent the braided structure from unraveling. The end bandscan also electrically couple the wires together. The bands though aresufficiently narrow so as not to meaningfully degrade the flexibility ofthe ablation element. Any braided pattern can work, but a “diamond”pattern mesh is preferred. The wires of the braid can either haverectangular (“flat”) or rounded cross sections. The wire material can beany of a wide variety of known biocompatible materials (such as thoseidentified above in connection with the coil electrodes). In one mode,the braided electrode can be “wounded” before inserting into the tubularporous membrane. Once inserted, the electrode can be uncoiled to pressagainst the inner surface of the tube. In this manner, the membrane cansupport the electrode.

An electrode can be constructed where the electrode is formed from aflat wire mesh that has been rolled into an arcuate structure. Thestructure may have a semi-cylindrical shape; however, the structure canextend through either more or less of an arc. Alternatively, theelectrode may have a “fishbone” pattern, wherein the electrode includesa plurality of arcuate segments that extend from an elongated sectionwhich generally lie parallel to a longitudinal axis of the ablationmember when assembled. The ends of each arcuate segment can be squaredor rounded.

An electrode may also be formed in an “arches” pattern. A plurality ofarch segments lie in series with two side rails interconnecting thecorresponding ends of the arch segments. The arch segments are spacedapart from one another along the length of the electrode. Suchembodiments can be formed by etching or laser cutting a tube ofelectrode material.

Common to all of the electrodes is the ability to flex. The flexibilityof these electrodes allows them to bend through tight turns in thevenous or arterial access path without collapsing. The electrodes alsohave low profiles so as to minimize the outer diameter of the ablationmember. Fluid can also pass radially through the electrodes. Other typesof electrode designs that exhibit these features can also be used. Forexample, the electrode can be formed in a manner resembling aconventional stent by etching or laser cutting a tube. The electrodealso need not extend entirely about the longitudinal axis of theablation member; the electrode can be generally flat and positioned ononly one side of the catheter. A serpentine shape would provide such aflat electrode with the desired flexibility. However, in order for theablation member to be less orientation sensitive, each electrodedesirably extends through at least 180 degrees about the longitudinalaxis of the ablation member. Accordingly, the foregoing electrodedesigns are merely exemplary of the types of electrodes that can be usedwith the present ablation member.

Although the following variations of the irrigation ablation member aredescribed as including a coiled electrode, it is understood that any offoregoing designs, as well as variations thereof, can be used as wellwith these devices.

The tissue ablation device assembly also desirably includes feedbackcontrol. For instance, the ablation member can include one or morethermal sensors (e.g., thermocouples, thermisturs, etc.) that areprovided to either the outer side or the inside of the porous membrane.Monitoring temperature at this location provides indicia for theprogression of the lesion. The number of thermocouples desirably equalsthe number of electrodes so as to enhance the independent control ofeach electrode. If the temperature sensors are located inside the porousmembrane, the feedback control may also need to account for anytemperature gradient that occurs across the membrane.

The sensors placed on the exterior of the porous member may also be usedto record electrogram signals by reconnecting the signal leads todifferent input port of the signal-processing unit. Such signals can beuseful in mapping the target tissue both before and after ablation.

In the one embodiment, the temperature sensors each comprise an annularthermocouple that is positioned about the outer side of the porousmembrane. In this location, the thermocouple lies on the outside of themembrane where it can directly contact the tissue-electrode interface.The thermocouple is isolated from direct metal-to-metal electricalcontact with the electrodes because the thermocouples are separated bythe porous membrane. Thus, separate insulation is not necessary.

The thermocouples desirably are blended into the outer surface of theablation member in order to present a smooth profile. Transition regionsformed by either adhesive or melted polymer tubing, “smooth out” thesurface of the ablation member as the surface steps up from the porousmember outer surface to the thermocouple surface.

Signal wires extend proximally from the thermocouples to the electricalconnector on the proximal end of the tissue ablation device assembly. Inthe illustrated mode, the wires are shielded and extend into the porousmembrane and then into the electrical lead tube. These wires can berouted proximally in other manners. For instance, the wires can form abraided structure on the exterior of the ablation member and then bepulled together and routed proximally along the side of the elongatedbody. The wires can also be routed proximally inside one or more tubesthat extend parallel to and are attached to the elongated body. Thewires can also be sewn into the wall of the outer tubing of theelongated body. These represent a few variations on various ways ofrouting the thermocouple wires to the proximal end of the tissueablation device assembly.

In use, the electrical and fluid connectors of the proximal coupler areconnected to the ablation actuator and the pressurized fluid source,respectively. A conventional grounding patch or other grounding deviceis placed against the patient.

The ablation member can be constructed in other forms while obtainingthe above-noted advantages. For instance, the ablation member caninclude a different shaft construction from that described above. Theballoon anchor wire and guidewire tubes may extend longitudinallythrough the ablation member positioned within a structure of braidedwires. Each of the wires is insulated, and the wires desirably are wovenin a diamond-like pattern.

The braided structure desirably includes at least an inner or an outercoating of a plastic material so as to define a pressurizable fluidpassageway. An inner layer and an outer layer of polymer are laminatedover the braid structure to define a generally fluid-impermeablestructure. The polymer layers stop at the distal end of the elongatedbody though. The braided structure continues distally to form a supportstructure for the ablation member. Fluid can pass through the uncoatedbraided structure.

The braided structure supports the electrodes. The electrodes are spacedalong the length of the braided structure to define the linear ablationelement. One of the wires from the braid is connected to a correspondingelectrode. Any of the above-described connectors can be used toelectrically couple an unshielded end of the conductor wire to thecorresponding electrode.

A spacer may be placed between adjacent electrode pairs to prevent fluidfrom flowing through a corresponding section of the braided structurenot covered by an electrode. The spacers can be formed of a polymer oran epoxy attached directly to the braided structure. The absence of aspacer, however, provides a fluid flow between the electrodes that maybe beneficial in some applications.

The porous membrane covers the electrodes supported by the braidedstructure. A proximal end of the porous membrane is secured to thedistal end of the elongated body, as defined by the distal end of thelaminate structure. The proximal end of the porous membrane can beattached in any of the above-described manners.

Similarly, the distal end of the porous membrane is attached to an endcap. The end cap includes an elongated collar that receives a distal endof the braided structure. The distal end of the porous membrane extendsover the collar and is secured thereto in any of the above-describedmanners.

The ablation member can also include one or more thermocouples. Thethermocouples are attached to the porous membrane in the mannerdescribed above. The thermocouple wires extend through the membrane andthrough the braided structure, and are routed proximally through theinner lumen of the braided structure that defines the pressurizablefluid passageway. The proximal ends of the thermocouple wires areconnected to an electrical connector of a proximal coupler.

Another variation of the ablation member involves an extruded shaftincluding a plurality of lumens. The shaft can be formed of Pebax oranother suitably flexible thermoplastic. The shaft includes four lumens:a first guidewire lumen, a second guidewire lumen, a fluid lumen, and anelectrical lead lumen. Although the lumens are arranged in aside-by-side arrangement, two or more of the lumens can have a coaxialarrangement. Plugs close the distal ends of the electrical lead lumenand the fluid lumen.

The shaft supports the electrodes. The electrodes are spaced along thelength of the shaft to define the linear ablation element. A conductorlead extends through the wall of the shaft from the electrical leadlumen at a point near the corresponding electrode. Any of theabove-described connectors can be used to electrically couple anunshielded end of the conductor wire to the corresponding electrode.Each of the electrical leads is connected to the proximal couplerlocated at the proximal end of the tissue ablation device assembly.

The porous membrane covers the electrodes supported by extrusion shaft.A proximal end of the porous membrane is securely sealed about the outersurface of the shaft, and the distal end of the porous member issecurely sealed about the shaft at a point proximal of the distal end ofthe shaft. The ends of the porous membrane can be attached to the shaftin any of the above-described manners.

This variation of the ablation member can also include one or morethermocouples. The thermocouples are attached to the porous membrane inthe manner described above. In the illustrated variation, thethermocouple wires extend through the membrane and through a hole in theshaft that opens into the electrical lead lumen, and are routedproximally through the lumen. The proximal ends of the thermocouplewires are connected to an electrical connector of a proximal coupler.

The shaft also includes an opening located just distal of the annularattachment of the proximal end of the porous member to the shaft. Theopening extends from the fluid lumen and opens into an inner spacedefined within the porous membrane. In this manner, fluid can flow fromthe fluid lumen and into the inner space so as to pressurize the innerspace before passing through the membrane in the manner described above.

In each of the above-described variations of the ablation member, theporous membrane covers the electrodes. The porous membrane, however, canlie inside or beneath the electrodes while still providing an even flowpast each of the electrodes. This modification can be incorporated intoeach of the variations described above. Thus, for example, the porousmembrane located between the electrodes and the braided structure. Theporous membrane lies atop the braided structure. The electrodes areplaced about the braided structure and the porous membrane. The ablationmember desirably includes a reduced diameter section in which theelectrodes reside to maintain a generally uniform profile along thedistal end of the tissue ablation device assembly. Spacers can also bepositioned within this section to lie between adjacent pairs ofelectrodes. As noted above, such spacers prevent fluid from flowingthrough the porous membrane at locations other than those about which anelectrode is located. The ablation member, however, can be configuredwithout spacers so as to provide a fluid flow between adjacentelectrodes.

Further variations of the ablation member may include a design where thedistal end of the ablation member is open; however, it desirably has atapering diameter. The smaller diameter permits some pressure to buildwithin the fluid passageway such that at least some of the fluid withinthe passageway emanates radially through the braided structure and theporous membrane, and across the electrodes. The distal end also can berounded to ease tracking through a venous or arterial access path.

The braided structure form supports the porous membrane over its entirelength. Other support can also be used. For example, internal orexternal rings can be spaced at various points along the length of theporous membrane to support further the membrane. In the alternative, amandrel can also be used for this purpose. A proximal end of the mandrelcan be embedded with the laminate structure and project in the distally.

Alternatively, a fluid delivery tube is located within the braidedstructure and can be moved by its proximal end located outside thepatient, so as to vary the location of the distal end of the tube. Thedistal end of the tube includes one or more openings which allow fluidto be delivered by the tube into the pressurizable passageway. By movingthe distal end of the fluid tube, the amount of fluid flowing across aparticular electrode can be varied. To further promote this effect, thefluid tube can include baffles located on the proximal and distal sidesof the fluid openings. These baffles enhance a radial flow of the fluidthrough porous membrane. Of course, these features can also beincorporated into several of the other variations described above.

The foregoing describes variations of an ablation member used to formlinear ablations within a body space. The ablation member can beincorporated into a variety of delivery devices so as to locate andposition the ablation member within the body space. At least one of theproximal and distal ends of the ablation member desirably is connectedto the delivery device. That end is maneuverable within the body spaceby manipulating a proximal end of the delivery device.

In order to add the proper positioning of the ablation element withinthe porous membrane, the catheter tip and the porous membrane desirablyinclude indicia which correspond to each other once the distal end ofthe ablation member has been advanced to a point positioning it withinthe membrane. For in vivo applications, such indicia can take the formof radiopaque markers positioned at corresponding locations on thecatheter and the porous membrane (or another location on the sheath).

Positioning System

The positioning system of FIG. 6 illustrates the relationship among atranseptal sheath 82, a preshaped guiding introducer 10 and adeflectable guidewire 30. The deflectable guidewire 30 is shown passingthrough and slideably engaged within the preshaped guiding introducer10. The distal end 84 of the deflectable guidewire 30 is aimed by thepreshaped guiding introducer 10 toward a predetermined pulmonary vein.The distal end 84 can be deflected 86 (shown in shadow) to steer theguidewire into the first or second pulmonary vein and/or to anchor theguidewire within the pulmonary vein. In one variation, the guidewire isa balloon anchor wire having an inflatable balloon at the distal end ofthe guidewire. The balloon anchor wire may be advanced through thepreshaped guiding introducer 10 and into a pulmonary vein. Subsequently,the balloon is inflated and the guiding introducer 10 is removed, byretraction over the anchored balloon, by peeling away, where the guidingintroducer has a longitudinal slit, or by any other method known in theart.

A preferred variation of the positioning system of the present inventionis shown in situ in FIG. 7. The transeptal sheath 82 traverses theatrial septum 90 that separates the right and left atria. The distal end92 of the transeptal sheath opens into the left atrium. Emerging fromthe transeptal sheath and slideably engaged therein is the ablationcatheter 94. The. distal end 96 of the ablation catheter 94 is shownengaging a first ostium 98 of a first pulmonary vein 100. A balloonanchor wire 102, having a balloon 104 on its distal end 106 is slideablyengaged within the ablation catheter 94, exiting the catheter throughthe first guidewire port 99. The balloon anchor wire 102 may have beenpositioned within the first pulmonary vein as described above, or asdetailed in pending U.S. Provisional application Ser. No. 60/113,610,herein incorporated in its entirety by reference thereto. The balloon104 is located within the first pulmonary vein 100 and inflated so as toanchor the ablation catheter 94 in position within the first ostium 98of the first pulmonary vein 100. Consequently, the distal end 108 of alinear ablation element 110 is secured against the atrial wall at alocation where the first pulmonary vein 100 extends from the atrium.

A preshaped guiding introducer 10, having a longitudinal slit 20 topermit peel-away removal, is shown emerging from a second guidewire port112 in the ablation catheter 94. The second guidewire port 112 islocated proximal to the proximal end 114 of the ablation element 110.The distal orifice 22 of the preshaped guiding introducer is manipulatedto point toward, or optionally reside within, the second ostium 116 ofthe second pulmonary vein 118. A second guidewire 120, slideably engagedwithin the preshaped guiding introducer 10, is positioned within thesecond pulmonary vein 118. By tracking distally over the preshapedguiding introducer 10 and/or the guidewire 120, the proximal end 114 ofthe ablation element 110 can be positioned and secured at a locationwhere the second pulmonary vein 118 extends from the atrium. Thepreshaped guiding introducer 10 can optionally be removed after theguidewire 120 has been positioned within the pulmonary vein 118. Removalof the guiding introducer 10 may be accomplished by retraction and/orpeeling away as described above.

Another variation of the positioning system of the present invention isshown in situ in FIG. 8. Again, the transeptal sheath 82 traverses theatrial septum 90 that separates the right and left atria. The distal end92 of the transeptal sheath opens into the left atrium. Emerging fromthe transeptal sheath and slideably engaged therein is the ablationcatheter 94. The distal end 96 of the ablation catheter 94 is shownengaging a region of tissue, for example, a first ostium 98, where thefirst pulmonary vein 100 extends from the atrium. A balloon anchor wire102, having a balloon 104 on its distal end 106 is slideably engagedwithin the ablation catheter 94. The balloon 104 is located within thefirst pulmonary vein 100 and inflated so as to anchor the ablationcatheter 94 in position within the first ostium 98 of the firstpulmonary vein 100. Consequently, the distal end 108 of the linearablation element 110 is secured at a location where the first pulmonaryvein 100 extends from the atrium.

A deflectable guidewire 30 is shown emerging from the second guidewireport 112 in the ablation catheter 94. The deflectable guidewire 30 isslideably engaged within the ablation catheter 94 and the distal end 122is adapted to be steerable by manipulating a pullwire (not shown) at theproximal end of the guidewire. Preferably, the deflectable guidewire 30is advanced into the second pulmonary vein 118 and anchored therein bydeflection of the distal end 122. By tracking over the deflectableguidewire 30, the proximal end 114 of the ablation element 110 can bepositioned and secured at a location, for example, the second ostium116, where the second pulmonary vein 118 extends from the atrium. Thedeflectable guidewire 30 may have been positioned within the secondpulmonary vein using a preshaped guiding introducer as described above.

Method of Using the Positioning System of the Present Invention

A patient diagnosed with atrial fibrillation due to perpetuallywandering reentrant wavelets originating from an arrhythmogenic originor focus in the left atrium and more particularly in a pulmonary veinmay be treated with a tissue ablation device assembly of the presentinvention by using the assembly to form a longitudinal conduction blockalong a path of the wall tissue of the pulmonary vein that eitherincludes the arrhythmogenic origin or is between the origin and the leftatrium. In the former case, the conduction block destroys thearrhythmogenic tissue at the origin as it is formed through that focus.In the latter case, the arrhythmogenic focus may still conductabnormally, although such aberrant conduction is prevented from enteringand affecting the atrial wall tissue due to the intervening conductionblock.

In positioning the ablation element at the ablation region, anintroducer sheath is first positioned within the left atrium accordingto a transeptal access method, which will be described in more detailbelow, and through the fossa ovalis. The right venous system is firstaccessed using the “Seldinger” technique, wherein a peripheral vein(such as a femoral vein), is punctured with a needle and the puncturewound is dilated with a dilator to a size sufficient to accommodate anintroducer sheath. An introducer sheath that has at least one hemostaticvalve is seated within the dilated puncture wound while relativehemostasis is maintained. With the introducer sheath in place, a guidingcatheter is introduced through the hemostatic valve of the introducersheath and is advanced along the peripheral vein, into the region of thevena cavae, and into the right atrium.

Once in the right atrium, the distal tip of the guiding catheter ispositioned against the fossa ovalis in the intra-atrial septal wall. A“Brochenbrough” needle or trocar is then advanced distally through theguiding catheter until it punctures the fossa ovalis. A separate dilatorcan also be advanced with the needle through the fossa ovalis to preparean access port through the septum for seating the transeptal sheath.Thereafter, the transeptal sheath replaces the needle across the septumand is seated in the left atrium through the fossa ovalis, therebyproviding access for object devices through its own inner lumen and intothe left atrium.

It is also contemplated that other left atrial access methods may beutilized for using the positioning system of the present invention. Inone alternative variation, a “retrograde” approach may be used, whereina guiding catheter is advanced into the left atrium from the arterialsystem. In this variation, the Seldinger technique is employed to gainvascular access into the arterial system, rather than the venous system,such as at a femoral artery. The guiding catheter is advancedretrogradely through the aorta, around the aortic arch, into the leftventricle, and then into the left atrium through the mitral valve.

After gaining access to the left atrium, a balloon anchor wire or otherguidewire is advanced into a first predetermined pulmonary vein. This isgenerally done through a preshaped guiding introducer which is coaxialwithin the transeptal sheath seated in the fossa ovalis, such as forexample, the preshaped guiding introducers described in FIGS. 1-3, or byusing a deflectable guidewire or catheter such as those described inFIGS. 4-5, or those disclosed in U.S. Pat. No. 5,575,766 to Swartz.Alternatively, the guidewire may have sufficient stiffness andmaneuverability in the left atrial cavity to unitarily select thedesired pulmonary vein distally of the transeptal sheath seated at thefossa ovalis.

The guidewire, balloon anchor wire or deflectable guidewire may bepreloaded within the guiding introducer or inserted into the proximalend of the guiding introducer after it has been positioned.Subsequently, the guidewire is advanced through the guiding introduceruntil the distal end exits the distal orifice of the guiding introducer,the guidewire being aimed by the guiding introducer toward the firstpulmonary vein.

The balloon anchor wire or other guidewire is then advanced into thefirst pulmonary vein to a suitable anchoring position. The fixedcorewire variation of the balloon anchor wire is directly advanced intothe first pulmonary vein. Alternatively, where the over-the-wirevariation is used, the guidewire is advanced into the pulmonary veinfirst and then the tubular member with the distal balloon follows,tracking over the guidewire and into the pulmonary vein. Anchoring ofthe guidewire is accomplished in either case by inflating the balloon toa predetermined air pressure or volume of a saline/contrast mixture.Where a deflectable guidewire is employed, the distal region of theguidewire is deflected after it is positioned well within the pulmonaryvein. Effective anchoring is tested by gently tugging on the guidewire.If the guidewire is not sufficiently anchored, the balloon is deflatedor the deflection released, and the wire is advanced further into thepulmonary vein or one of its branches. Inflating and/or deflecting,testing and repositioning are performed in this manner until theguidewire is sufficiently anchored. If necessary the balloon anchor wireor deflectable guidewire may be advanced into a different branch of thefirst pulmonary vein to find a secure anchoring position.

Once the guidewire is securely anchored, the shaped guiding introducermay be retracted back through the transeptal sheath and removed. Thepeel-away variety may be partially retracted and then peeled away fromthe guidewire. Alternatively, where the proximal end of the balloonanchor wire has a removable Y-adapter (inflation/deflation hub), theY-adapter is removed by releasing the pressure on the balloon, looseningthe distal and proximal O-ring knobs on the adapter, and sliding theadapter off the balloon anchor wire. Care must be taken not to displacethe balloon on the distal end of the anchor wire when removing theadapter from the proximal end of the anchor wire. Once the Y-adapter hasbeen removed, the guiding introducer may be withdrawn completely bysliding it off the proximal end of the balloon anchor wire.

The ablation catheter, which is adapted to slideably engage the balloonanchor wire or other guidewire, is then slid over the proximal end ofthe guidewire. Once the ablation catheter is advanced past the proximalend of the balloon anchor wire, the Y-adapter is reattached and theballoon is reinflated. Similarly, where a deflectable guidewire with aremovable handle, like that illustrated in FIG. 5, is employed, thehandle is reattached once the ablation catheter is advanced past theproximal end of the deflectable guidewire. The distal end of can then bedeflected again to anchor the guidewire. The user should gently tug onthe guidewire to insure that it is still securely anchored in the firstpulmonary vein.

The ablation catheter is then advanced over the guidewire, through thetranseptal sheath, and continuing until the distal end of the ablationcatheter, including the distal end of the ablation element, engages thefirst pulmonary vein ostium. A combination of pushing and pullingalternatively on both the guidewire and the ablation catheter may beemployed to facilitate advancement of the ablation catheter. In avariation of the method, a stylet may be placed inside the ablationcatheter to further assist in advancing it along the guidewire towardthe first pulmonary vein ostium. Once the distal end of the ablationcatheter engages.the first pulmonary vein ostium and is securely seatedtherein, the proximal portions of the ablation catheter, including theproximal end of the ablation element, are further advanced into the leftatrium, causing the ablation catheter to prolapse against the atrialwall. If a stylet was used inside the ablation catheter to facilitateadvancement and positioning of the ablation catheter, retracting thestylet now may permit the catheter to conform more readily to the atrialwall.

Where a second guidewire is being employed to facilitate positioning ofthe proximal end of the ablation element, the guidewire is advanced intoa second pulmonary vein prior to prolapsing the ablation catheteragainst the atrial wall. This is preferably accomplished by advancing apreshaped guiding introducer, which was preloaded within the ablationcatheter, distally through the second guidewire passageway in theablation catheter until the curved distal end of the guiding introduceremerges from the second guidewire port, located proximal to the proximalend of the ablation element. The guiding introducer can then beadvanced, retracted and/or torqued in such a manner as to cause thedistal orifice of the guiding introducer to point toward the secondostium of the second pulmonary vein. In one variation, the guidingintroducer can be advanced into the pulmonary vein. The second guidewireis then advanced through the guiding introducer into the pulmonary vein.The deflectable guidewire may be used alone within the second guidewirepassageway or may be slideably engaged within a guiding introducer asdescribed above.

Once the guidewire is in place within the second pulmonary vein, theproximal end of the ablation element is advanced more accurately towardthe second pulmonary vein ostium by tracking along the guidewire. Asdescribed above a stylet may be employed within the ablation catheter topush the proximal end of the ablation element toward the second ostiumof the second pulmonary vein.

Delivery of RF energy to the endocardial tissue of the pulmonary vein iscommenced once the ablation member is positioned at the desired ablationregion. Good contact between the ablation element and the underlyingtissue facilitates the creation of a continuous transmural lesion. RFenergy from the ablation actuator is delivered to electrodes viaelectrical leads. The ablation actuator desirably includes a currentsource for supplying a RF current, a monitoring circuit, and a controlcircuit. The current source is coupled to the linear ablation elementvia a lead set, and to a ground patch. The monitor circuit desirablycommunicates with one or more sensors (e.g., temperature or currentsensors) which monitor the operation of the linear ablation element. Thecontrol circuit is connected to the monitoring circuit and to thecurrent source in order to adjust the output level of the currentdriving the electrodes of the linear ablation element based upon thesensed condition (e.g., upon the relationship between the monitoredtemperature and a predetermined temperature set point).

At the same time, conductive fluid, such as saline, is directed into thefluid coupler and through the fluid lumen. In some instances, it may bedesirable to begin to apply positive fluid pressure even before RFablation is commenced in order to prevent blood accumulation in or onthe ablation member.

In one variation, the saline passes through openings in the fluid tubingto an inner space within the porous membrane. When the pressure withinthe inner space reaches a predetermined pressure, the fluid weeps out ofthe porous membrane. The fluid can be uniformly distributed along thelongitudinal length of the ablation element because the fluid does notimmediately flow through the porous membrane, but instead remains withinthe inner space until the predetermined pressure is reached. Thisprovides for both a uniform flow of fluid through the length of theporous membrane and a uniform flow of RF energy along the ablationelement. That is, the porous membrane diffuses the saline across eachindividual electrode, as well as across the array of electrodes. Whilethe conductive fluid or saline is used to create a uniform conductivepath between the electrodes and the target tissue, the saline can bealternatively or additionally utilized to cool the ablation electrodes.The fluid flows both through the helical coil of the ablation elementand between the plurality of ablation elements of the ablation member,thereby facilitating the cooling of the electrodes by the fluid. Thebath of saline may possibly cool the electrodes so as to be capable ofdelivering high levels of current or be capable of longer durations toproduce deeper lesions.

Once a lesion has been formed along the target length, the ablationcatheter may be repositioned and additional lesions formed.

In accordance with another mode of the ablation catheter, an ultrasoundsonically couples with the outer skin of the balloon in a manner thatforms a circumferential conduction block in a pulmonary vein as follows.FIG. 9 shows an ablation catheter in accordance with this mode of thepresent invention. An ultrasound transducer is located along the distalend portion of the catheter shaft within an inflatable balloon.Initially, the ultrasound transducer is believed to emit its energy in acircumferential pattern that is highly collimated along the transducer'slength relative to its longitudinal axis L. The circumferential bandtherefore maintains its width and circumferential pattern over anappreciable range of diameters away from the source at the transducer.Also, the balloon is preferably inflated with fluid that is relativelyultrasonically transparent, such as, for example, degassed water.Therefore, by actuating the transducer while the balloon is inflated,the circumferential band of energy is allowed to translate through theinflation fluid and ultimately sonically couple with a circumferentialband of balloon skin which circumscribes the balloon. Moreover, thecircumferential band of balloon skin material may also be furtherengaged along a circumferential path of tissue which circumscribes theballoon, such as, for example, if the balloon is inflated within andengages a pulmonary vein wall, ostium, or region of atrial wall.Accordingly, where the balloon is constructed of a relativelyultrasonically transparent material, the circumferential band ofultrasound energy is allowed to pass through the balloon skin and intothe engaged circumferential path of tissue such that the circumferentialpath of tissue is ablated.

While a number of variations of the invention have been shown anddescribed in detail, other modifications and methods of use contemplatedwithin the scope of this invention will be readily apparent to those ofskill in the art based upon this disclosure. It is contemplated thatvarious combinations or subcombinations of the specific embodiments maybe made and still fall within the scope of the invention. For example,the embodiments variously shown to be “guidewire” tracking variationsfor delivery into a left atrium and around or within a pulmonary veinmay be modified to instead incorporate a deflectable/steerable tipinstead of guidewire tracking and are also contemplated. Moreover, allassemblies described are believed useful when modified to treat othertissues in the body, in particular other regions of the heart, such asthe coronary sinus and surrounding areas. Further, the disclosedassemblies may be useful in treating other conditions, wherein aberrantelectrical conduction may be implicated, such as for example, heartflutter. Indeed, other conditions wherein catheter-based, directedtissue ablation may be indicated, such as for example, in the ablationof fallopian tube cysts. Accordingly, it should be understood thatvarious applications, modifications and substitutions may be made ofequivalents without departing from the spirit of the invention or thescope of the following claims.

What is claimed is:
 1. A positioning system for guiding a catheter to alocation where a pulmonary vein extends from an atrium, comprising adeflection device, a sheath adapted to be deflected by the deflectiondevice, and a guidewire, wherein the deflection device can be removablyengaged within the sheath and wherein the deflection device and thesheath cooperate to facilitate positioning of the guidewire within thepulmonary vein when the guidewire is advanced through the sheath andinto the atrium.
 2. The positioning system of claim 1, wherein thedeflection device comprises a pre-shaped stylet.
 3. The positioningsystem of claim 1, wherein the deflection device comprises a pre-shapedtubular guide member.
 4. The positioning system of claim 1, wherein thedeflection device is integral with the sheath.
 5. The positioning systemof claim 4, wherein the sheath further comprises proximal and distalends and a moveable pullwire attached to the distal end of the sheath,and wherein the proximal end of the sheath is adapted to facilitatemanipulation of the pullwire, such that manipulation of the pullwirecauses deflection of the distal end of the sheath.
 6. The positioningsystem of claim 1, wherein the deflection device is integral with thecatheter.
 7. The positioning system of claim 6, wherein the catheterfurther comprises proximal and distal ends and a moveable pullwireattached to the distal end of the catheter, and wherein the proximal endof the catheter is adapted to facilitate manipulation of the pullwire,such that manipulation of the pullwire causes deflection of the distalend of the catheter.
 8. The positioning system of claim 1, wherein thecatheter further comprises an electrode element.
 9. The positioningsystem of claim 8, wherein the electrode element comprises a mappingelectrode.
 10. The positioning system of claim 8, wherein the electrodeelement comprises an ablation electrode.
 11. The positioning system ofclaim 8, wherein the electrode element comprises both a mappingelectrode and an ablation electrode.
 12. The positioning system of claim8, wherein the electrode element is an RF ablation element.
 13. Thepositioning system of claim 1, wherein the catheter further comprises anablation element.
 14. The positioning system of claim 13, wherein theablation element comprises a microwave ablation element.
 15. Thepositioning system of claim 13, wherein the ablation element comprises acryogenic ablation element.
 16. The positioning system of claim 13,wherein the ablation element comprises a thermal ablation element. 17.The positioning system of claim 13, wherein the ablation elementcomprises a light-emitting ablation element.
 18. The positioning systemof claim 13, wherein the ablation element comprises an ultrasoundtransducer.
 19. The positioning system of claim 13, wherein the ablationelement is adapted to form a linear lesion.
 20. The positioning systemof claim 13, wherein the ablation element is adapted to form acircumferential lesion.
 21. The positioning system of claim 20, whereinthe ablation element is adapted to form the circumferential lesion atthe location.
 22. The positioning system of claim 1, wherein theguidewire is selected from the group consisting of a guidewire, ananchor wire, and a deflectable guidewire.
 23. The positioning system ofclaim 22, wherein the anchor wire comprises a elongate body withproximal and distal end portions and having an expandable member alongthe distal end portion, such that radial expansion of the expandablemember is adapted to anchor the guidewire within the pulmonary vein. 24.A positioning system for guiding an ablation catheter to a locationwhere a lumen extends from a body cavity, comprising a deflection deviceand a sheath having an opening at a distal end, the ablation catheterbeing independently advanceable through the sheath and out the distalend, wherein the deflection device can be removably engaged within thesheath and wherein the deflection device and the sheath cooperate tofacilitate positioning of the ablation catheter at the location when thecatheter is advanced through the sheath and into the body cavity andguided toward the location.
 25. The positioning system of claim 24,wherein the deflection device comprises a pre-shaped stylet.
 26. Thepositioning system of claim 24, wherein the deflection device comprisesa pre-shaped tubular guide member.
 27. The positioning system of claim24, wherein the deflection device is integral with the sheath.
 28. Thepositioning system of claim 27, wherein the sheath further comprisesproximal and distal ends and a moveable pullwire attached to the distalend of the sheath, and wherein the proximal end of the sheath is adaptedto facilitate manipulation of the pullwire, such that manipulation ofthe pullwire causes deflection of the distal end of the sheath.
 29. Thepositioning system of claim 24, wherein the deflection device isintegral with the ablation catheter.
 30. The positioning system of claim29, wherein the ablation catheter further comprises proximal and distalends and a moveable pullwire attached to the distal end of the ablationcatheter, and wherein the proximal end of the catheter is adapted tofacilitate manipulation of the pullwire, such that manipulation of thepullwire causes deflection of the distal end of the catheter.
 31. Thepositioning system of claim 24, wherein the ablation catheter has anablation element.
 32. The positioning system of claim 31, wherein theablation element comprises a microwave ablation element.
 33. Thepositioning system of claim 31, wherein the ablation element comprises acryogenic ablation element.
 34. The positioning system of claim 31,wherein the ablation element comprises a thermal ablation element. 35.The positioning system of claim 31, wherein the ablation electrodecomprises a light-emitting ablation element.
 36. The positioning systemof claim 31, wherein the ablation element comprises an ultrasoundtransducer.
 37. The positioning system of claim 31, wherein the ablationelement is an RF ablation element.
 38. The positioning system of claim31, wherein the ablation element is adapted to form a linear lesion. 39.The positioning system of claim 31, wherein the ablation element isadapted to form a circumferential lesion.
 40. The positioning system ofclaim 39, wherein the ablation element is adapted to form thecircumferential lesion at the location.
 41. A positioning system forguiding an ablation catheter to a location where a pulmonary veinextends from an atrium, comprising a deflection device and a transeptalsheath having proximal and distal ends, wherein the deflection device isremovably positionable within the transeptal sheath without extendingbeyond the distal end of the sheath.
 42. The positioning system of claim41, wherein the deflection device comprises a pre-shaped stylet.
 43. Thepositioning system of claim 41, wherein the deflection device comprisesintegral with the sheath.
 44. The positioning system of claim 43,wherein the sheath further comprises proximal and distal ends and amoveable pullwire attached to the distal end of the sheath, and whereinthe proximal end of the sheath is adapted to facilitate manipulation ofthe pullwire, such that manipulation of the pullwire causes deflectionof the distal end of the sheath.
 45. A positioning system for placing alinear ablation element in contact with a length of tissue along anatrial wall, comprising: a transeptal sheath having a distal port, thetranseptal sheath being adapted for traversing an atrial septum; a firstguiding introducer adapted for slidable advancement through thetranseptal sheath and out the distal port; a first guidewire adapted forslidable advancement through the guiding introducer, the guidingintroducer being shaped to direct the first guidewire toward a firstpulmonary vein, the first guidewire having an expandable balloondisposed along a distal end portion and adapted for engagement with thefirst pulmonary vein; an ablation catheter adapted for advancement overthe first guidewire and into the left atrium, the ablation catheterhaving the linear ablation element disposed along a distal end portionand a side port located proximal to the ablation element; and a secondguidewire adapted for advancement through the ablation catheter and outthrough the side port for insertion into a second pulmonary vein forengagement therein.
 46. The positioning system of claim 45, furthercomprising a second guiding introducer which is advanceable through theablation catheter and out the side port for facilitating the advancementof the second guidewire into the second pulmonary vein.
 47. Thepositioning system of claim 45, wherein the second guidewire isdeflectable for facilitating advancement out the side port and into thesecond pulmonary vein.